 function s1_generate_a_series_of_files(){
 for i in {1..100};do echo $i>/tmp/new_file$i;done
 }
 function s2_list_4_files_in_long_format_about_account_and_group(){
 ls -l /etc/{passwd,shadow,group,gshadow} |sort -d
 }
 function s3_find_items_related_to_given_username(){
 grep -h $1 /etc/{group,gshadow} |sort -d
 }
 function s4_find_items_related_to_given_group_name(){
 grep -h $1 /etc/{group,gshadow} |sort -d
 }
 function s5_create_groups_for_given_group_names(){
 groupadd rnd && groupadd itoperation
 }
 function s6_create_users_and_set_their_group_as_required(){
 useradd -G rnd adam && useradd -G rnd bob  && useradd -G itoperation  calvin  && useradd -G itoperation david
 }
 function s7_change_users_shell(){
 usermod -s /usr/bin/sh adam && usermod -s /usr/bin/sh edward
 }
 function s8_set_password_change_policy(){
 passwd -n 10 -x 60 -w 10 adam
 passwd -n 10 -x 60 -w 10 bob
 passwd -n 10 -x 60 -w 10 david
 passwd -n 10 -x 60 -w 10 calvin
 passwd -n 10 -x 60 -w 10 edward
 }
 function s9_set_password_for_five_users(){
 usernames=(adam bob calvin david edward)
 for i in $(seq 1 5);do echo ${!i};echo $(( $i-1 ));done
 echo "${usernames[0]}:$1" | chpasswd
 echo "${usernames[1]}:$2" | chpasswd
 echo "${usernames[2]}:$3" | chpasswd
 echo "${usernames[3]}:$4" | chpasswd
 echo "${usernames[$(( $i-1 ))]}:$5" | chpasswd
 }
 function s10_lock_bobs_password(){
 usermod -L bob
 }
 function s11_include_adam_into_wheel_group(){
 usernod -a -G wheel adam
 }
 function s12_change_files_permission(){
 for i in {1..33};do chmod -R 640 /tmp/new_file$[3*i];done
 }

